A large new study by a team of international researchers has identified shared genetic associations between irritable bowel syndrome and mental health conditions such as anxiety and depression.
The study, published in the journal Nature, used data from more than 50,000 people with irritable bowel syndrome (IBS) and found that its symptoms may be caused by the same biological processes that trigger anxiety, depression, and insomnia.
Shared Genetic Origin
While the study highlights the interconnections between the brain and digestive health, the researchers said that the findings don’t mean that anxiety or mood disorders cause IBS, or that IBS causes anxiety and mood disorders. Rather, that certain genes are involved in the progression of both conditions.
“Although IBS occurs more frequently in those who are prone to anxiety, we don’t believe that one causes the other,” said Professor Miles Parkes of the University of Cambridge, who was a co-senior investigator and consulting gastroenterologist on this research. “Our study shows these conditions have shared genetic origins, with the affected genes possibly leading to physical changes in brain or nerve cells that in turn cause symptoms in the brain and symptoms in the gut.”
Past studies have shown that anxiety and depression often go hand-in-hand with IBS, but this study showed that these associations are because of actual shared genetic processes and not because someone may become depressed or anxious because of having IBS.
Common Conditions
IBS and anxiety are both quite common. In the U.S. estimates are that about 20 percent of adults experience an anxiety disorder, meaning their anxiety has caused mild to severe impairment of their day-to-day lives. It is estimated that worldwide about one in 10 people are affected by IBS. Symptoms of IBS include abdominal pain, bloating or bowel dysfunction significant enough to interfere with day-to-day activity. The causes of IBS are not well understood. But it tends to run in families and is more common in people who are prone to anxiety and other mood disorders.
For this study, the team of researchers from 40 different institutions identified different loci in six genes associated with IBS. Loci in four of those genes were also associated with mood and anxiety disorders. The researchers first used data from both the UK Biobank and the Bellygenes Initiative — a worldwide study looking at genetic links to IBS. All the data came primarily from people of European ancestry, and the researchers used data from another 400,000 individuals who do not have IBS as a control group. The team then replicated their findings using de-identified data from 23andMe customers who consented to participate in research, which included more than 200,000 individuals with IBS and another 1.3 million who do not have the condition. The study also found a strong genome-wide correlation between the risk of IBS, and the risk for anxiety, neuroticism, and depression. Although IBS symptoms affect the gut and bowels, the genes associated with increased risk for IBS are not expressed there. Instead, they appear to have a clearer role in the brain, and possibly the network of nerves that serve the gut.
One of the paper’s lead authors, Chris Eijsbouts, of the University of Oxford, said the new research could aid in the development of new treatments in the future for these conditions.
“Even genetic changes that have only subtle effects on IBS can provide clues about pathways to target therapeutically,” Eiisbouts said. “Unlike the individual genetic changes themselves, drugs targeting the pathways they tell us about may have a considerable impact on the condition, as we know from other disease areas.”
Find the study in Nature here.